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Medical Dictionary


orchichorea (or′ke-ko-re′a)
Involuntary rising and falling movements of the testis. [orchi- + G. choreia, a dance]

orchidectomy (or-ki-dek′to-me)
SYN: orchiectomy.

orchidic (or-kid′ik)
Relating to the testis.

orchiditis (or-ki-di′tis)
SYN: orchitis.

See orchi-.

orchidometer (or-ki-dom′e-ter)
1. A caliper device used to measure the size of testes. 2. A set of sized models of testes for comparison of testicular development. [orchido- + G. metron, measure]

orchidopexy (or-kid′o-peks-&maer;e)
SYN: orchiopexy.

orchidoptosis (or′ki-dop-to′sis)
Ptosis of the male gonads. [orchido- + G. ptosis, a falling]

orchidorraphy (or-ki-dor′a-fe)
SYN: orchiopexy.

orchiectomy (or-ke-ek′to-me)
Removal of one or both testes. SYN: orchectomy, orchidectomy, testectomy. [orchi- + G. ektome, excision]

orchiepididymitis (or′ke-ep′i-did′i-mi′tis)
Inflammation of the testis and epididymis. [orchi- + epididymis, + G. -itis, inflammation]

orchil (or′kil) [old C.I. 1242]
SYN: archil.

See orchi-.

orchiocele (or′ke-o-sel)
A testis retained in the inguinal canal. [orchio- + G. kele, hernia, tumor]

orchiodynia (or′ke-o-din′e-a)
SYN: orchialgia. [orchi- + G. odyne, pain]

orchioncus (or-ke-ong′kus)
A neoplasm of the testis. [orchio- + G. onkos, bulk, mass]

orchioneuralgia (or′ke-o-noo-ral′je-a)
SYN: orchialgia. [orchio- + G. neuron, nerve, + algos, pain]

orchiopathy (or-ke-op′a-the)
Disease of a testis. [orchio- + G. pathos, suffering]

orchiopexy (or′ke-o-pek′se)
1. Surgical treatment of an undescended testicle by freeing it and implanting it into the scrotum. 2. Anchoring a testis susceptible to torsion in the scrotum. SYN: orchidopexy, orchidorraphy, orchiorrhaphy. [orchio- + G. pexis, fixation] transseptal o. SYN: Ombrédanne operation.

orchioplasty (or′ke-o-plas-te)
Surgical reconstruction of the testis. [orchio- + G. plastos, formed]

orchiorrhaphy (or-ke-or′a-fe)
SYN: orchiopexy. [orchio- + G. rhaphe, a suture]

orchiotherapy (or′ke-o-thar′a-pe)
Treatment with testicular extracts.

orchiotomy (or-ke-ot′o-me)
Incision into a testis. SYN: orchotomy. [orchio- + G. tome, incision]

orchis, pl .orchises (or′kis, or′ki-sez)
SYN: testis. [G. testis, an orchid]

orchitic (or-kit′ik)
Denoting orchitis.

orchitis (or-ki′tis)
Inflammation of the testis. SYN: orchiditis, testitis. [orchi- + G. -itis, inflammation] o. parotidea o. associated with mumps. traumatic o. simple inflammation of the testis caused by mechanical injury. o. variolosa o. complicating smallpox.

orchotomy (or-kot′o-me)
SYN: orchiotomy.

orcin (or′sin)
SYN: orcinol.

orcinol (or′sin-ol)
3,5-Dihydroxytoluene;the parent substance of the natural dye orcein, obtained from certain colorless lichens (Lecanora tinctoria, Rocella tinctoria) by treatment with boiling water; used as an external antiseptic in various skin diseases and in chemistry as a reagent for pentoses. SYN: 5-methylresorcinol, orcin.

orciprenaline sulfate (or-si-pren′a-len)
SYN: metaproterenol sulfate.

Abbreviation for optic rotatory dispersion.

Symbol for orotidine.

ordeal bean (or′de-al)
SYN: physostigma.

order (or′der)
1. In biologic classification, the division just below the class (or subclass) and above the family. 2. In a reaction, o. is the sum of the exponents of all the concentration terms in that reaction's rate expression. For example, for the natural decomposition of nitrogen pentoxide, the rate expression is v = −d[N2O5]/dt = k1[N2O5]. Thus, this is a first-o. reaction. A reaction involving two different compounds is often a second-o. reaction (but not necessarily so). Pseudo–first-o. reactions are multiorder reactions in which one of the reactants is in substoichiometric amounts. Cf.:molecularity. 3. The sequence of residues in a heteropolymer. [L. ordo, regular arrangement] pecking o. in some species of birds and primates, the establishment of a graded dominance in members of a group by the use of aggression.

ordered (ord′erd)
SYN: o. mechanism.

orderly (or′der-le)
An attendant in a hospital unit who assists in the care of patients.

ordinate (or′di-nat)
In a plane cartesian coordinate system, the vertical axis (y). Cf.:abscissa.

orectic (o-rek′tik)
Pertaining to or characterized by orexia.

orexia (o-rek′se-a)
1. The affective and conative aspects of an act, in contrast to the cognitive aspect. 2. SYN: appetite. [G. orexis, appetite]

orexigenic (o-rek-si-jen′ik)
Appetite stimulating.

A specific disease of sheep and goats, caused by the o. virus, family Poxviridae. This virus is transmissible to humans and characterized by vesiculation and ulceration of the infected site. SYN: contagious ecthyma, scabby mouth, soremouth. [O.E. orfcwealm, murrain, fr. o., cattle, + cwealm, destruction]

organ (or′gan) [TA]
Any part of the body exercising a specific function, as of respiration, secretion, or digestion. SYN: organum [TA] , organon. [L. organum, fr. G. organon, a tool, instrument] accessory organs 1. SYN: accessory structures, under structure. 2. SYN: supernumerary organs. accessory organs of the eye SYN: accessory visual structures, under structure. annulospiral o. SYN: annulospiral ending. auditory o. archaic term for Corti o.. Chievitz o. a normal epithelial structure, possibly a neurotransmitter, found at the angle of the mandible with branches of the buccal nerve. circumventricular organs four small areas in or near the base of the brain that have fenestrated capillaries and are outside the blood-brain barrier. They are neurohypophysis, area postrema [TA], organum vasculosum of lamina terminalis [TA], and subfornical o. [TA] (SFO). The neurohypophysis is a neurohemal o.. The other three are chemoreceptors: area postrema triggers vomiting in response to chemical changes in plasma, organum vasculosum of the lamina terminalis senses osmolality and alters vasopressin secretion, and SFO initiates drinking in response to angiotensin II. Corti o. SYN: spiral o.. critical o. the o. or physiologic system that for a given source of radiation would first reach its legally defined maximum permissible radiation exposure as the dose of radiation is increased; e.g., the kidney is the critical o., receiving the most radiation, when Tc-99m dimethylsuccinic acid is given. enamel o. a circumscribed mass of ectodermal cells budded off from the dental lamina; it becomes cup shaped and develops on its internal face the ameloblast layer of cells that produce the enamel cap of a developing tooth. end o. the special structure containing the terminal of a nerve fiber in peripheral tissue such as muscle, tissue, skin, mucous membrane, or glands. SEE ALSO: ending. external female genital organs SYN: female external genitalia. external male genital organs SYN: male external genitalia. floating o. SYN: wandering o.. flower-spray o. of Ruffini SYN: flower-spray ending. genital organs SYN: genitalia. Golgi tendon o. a proprioceptive sensory nerve ending embedded among the fibers of a tendon, often near the musculotendinous junction; it is compressed and activated by any increase of the tendon's tension, caused either by active contraction or passive stretch of the corresponding muscle. SYN: neurotendinous o., neurotendinous spindle. gustatory o. [TA] located in the papillae of the mucous membrane of the tongue, chiefly in the vallate papillae. SYN: organum gustatorium [TA] , organum gustus [TA] , o. of taste. o. of hearing SYN: cochlear labyrinth. internal female genital organs SYN: female internal genitalia. internal male genital organs SYN: male internal genitalia. intromittent o. SYN: penis. Jacobson o. SYN: vomeronasal o.. neurohemal organs brain areas from which substances enter blood e.g., the neurohypophysis from which oxytocin and vasopressin enter blood. neurotendinous o. SYN: Golgi tendon o.. olfactory o. [TA] the olfactory region in the superior portion of the nasal cavity. SYN: organum olfactus [TA] , o. of smell. otolithic organs the utricle and saccule of the inner ear that possess otoliths and respond to linear acceleration and deceleration, including gravity. ptotic o. SYN: wandering o.. o. of Rosenmüller SYN: epoophoron. sense organs [TA] the organs of special sense, including the eye, ear, olfactory o., taste organs, and the accessory structures associated with these organs. SYN: organa sensuum. o. of smell SYN: olfactory o.. spiral o. [TA] a prominent ridge of highly specialized epithelium in the floor of the cochlear duct overlying the basilar membrane of cochlea, containing one inner row and three outer rows of hair cells, or cells of Corti (the auditory receptor cells innervated by the cochlear nerve) supported by various columnar cells: the pillars of Corti, cells of Hensen, and cells of Claudius; the spiral o. is partly overhung by an awninglike shelf, the tectorial membrane, the free marginal zone of which is covered by a gelatinous substance in which the stereocilia of the outer hair cells are embedded. SYN: organum spirale [TA] , acoustic papilla, Corti o.. subcommissural o. [TA] a microscopic o., made up of columnar ciliated ependymal cells, located in the cerebral aqueduct beneath the posterior commissure of the brain; it is believed to have a neurosecretory function. SYN: organum subcommissurale. subfornical o. (SFO) the intercolumnar tubercle. One of the circumventricular organs. SFO has fenestrated capillaries and is outside the blood-brain barrier. It is thought to be a chemoreceptor zone involved in cardiovascular regulation. SYN: organum subformicale [TA] . supernumerary organs organs exceeding the normal number, which may develop from multiple foci of organization in an o.-formative field larger (originally) than that of the definitive main o.; such organs are aberrant but frequently not a cause of disease; illness may persist if they are left in the body after therapeutic removal of the main o., e.g., accessory spleen. SYN: accessory organs (2) . tactile o. SYN: o. of touch. target o. a tissue or o. upon which a hormone exerts its action; generally, a tissue or o. with appropriate receptors for a hormone. SYN: target (3) . o. of taste SYN: gustatory o.. o. of touch any one of the sensory end organs. SYN: organum tactus, tactile o.. urinary organs organs involved with the formation, storage, and excretion of urine. SEE ALSO: urinary system. SYN: organa urinaria. vascular o. of lamina terminalis [TA] See circumventricular organs. SYN: organum vasculosum laminae terminalis [TA] . vestibular o. SYN: vestibular labyrinth. vestibulocochlear o. [TA] the external, middle, and internal ear. SYN: organum vestibulocochleare [TA] . vestigial o. a rudimentary structure in humans corresponding to a functional structure or o. in the lower animals. o. of vision SYN: visual o.. visual o. the eye and its adnexa. SYN: o. of vision, organum visus. vomeronasal o. [TA] a fine vestigal horizontal canal, ending in a blind pouch, in the mucous membrane of the nasal septum, beginning just behind and above the incisive duct; a structure that usually regresses after the 6th month of gestation. In many lower animals, it functions as an accessory olfactory o.. SYN: organum vomeronasale [TA] , Jacobson o.. wandering o. an o. with loose attachments, permitting its displacement. SYN: floating o., ptotic o.. Weber o. SYN: prostatic utricle. organs of Zuckerkandl SYN: paraaortic bodies, under body.

organa (or′ga-na)
Plural of organum.

organelle (or′ga-nel)
One of the specialized parts of a protozoan or tissue cell; these subcellular units include mitochondria, the Golgi apparatus, nucleus and centrioles, granular and agranular endoplasmic reticulum, vacuoles, microsomes, lysosomes, plasma membrane, and certain fibrils, as well as plastids of plant cells. SYN: cell o., organoid (3) . [G. organon, organ, + Fr. -elle, dim. suffix, fr. L. -ella] cell o. SYN: o.. paired organelles SYN: rhoptry.

organic (or-gan′ik)
1. Relating to an organ. 2. Relating to or formed by an organism. 3. Organized; structural. 4. See o. compound. [G. organikos]

organicism (or-gan′i-sizm)
A theory that attributes all diseases, in particular, all mental disorders, as organic in origin.

organicist (or-gan′i-sist)
One who believes in, or subscribes to the views of, organicism.

SYN: iodinated glycerol.

organism (or′ga-nizm)
Any living individual, whether plant or animal, considered as a whole. calculated mean o. (CMO) a hypothetical o. whose characters are the means of both the positive and negative characters of the organisms which belong to the same taxon as the CMO, as opposed to the hypothetical mean. o.. defective o. SYN: auxotrophic mutant. fastidious o. a bacterial o. having complex nutritional requirements. hypothetical mean o. (HMO) a hypothetical o. whose characters are the means of the positive characters of the organisms which belong to the same taxon as the HMO, as opposed to the calculated mean o.. pleuropneumonia-like organisms (PPLO) the original name given to a group of bacteria that did not possess cell walls; these organisms, isolated from humans and other animals, soil, and sewage, are now assigned to the order Mycoplasmatales.

organization (or′gan-i-za′shun)
1. An arrangement of distinct but mutually dependent parts. 2. The conversion of coagulated blood, exudate, or dead tissue into fibrous tissue. health maintenance o. (HMO) a comprehensive prepaid system of health care intended to have emphasis on the prevention and early detection of disease, and continuity of care; often used synonymously with “managed care plan.”The term HMO refers to a health care delivery system characterized by multiplicity of services (primary care physicians and specialists, laboratory, radiology, pharmacy, and hospitalization); restriction of services to subscribers, and of benefits to participating health care providers, both typically confined to a certain geographic area; and an accounting system based on prepayment rather than fee for service. An HMO may be a nonprofit institution or a commercial venture. During the last quarter of the 20th century, HMOs emerged as an important alternative to traditional medical indemnity insurance plans, and largely supplanted them. HMOs have had a profound effect on every aspect of the practice of medicine: professional, scientific, social, economic, and legal. Some state legislatures, seeing the HMO's determining which medical services are appropriate in given circumstances as the practice of medicine, have passed laws rendering them liable to malpractice litigation. see also managed care. preferred provider o. (PPO) a health care delivery model that uses a panel of eligible physicians. pregenital o. in psychoanalysis, the o. or arrangement of the libido in the stages prior to that of genital primacy.

organize (or′gan-iz)
To provide with, or to assume, a structure.

organizer (or′gan-i-zer)
1. Originally applied to a group of cells on the dorsal lip of the blastopore, which induce differentiation of cells in the embryo and control growth and development of adjacent parts. 2. Any group of cells having such a controlling influence, the effects being brought about through the action of an evocator. nucleolar o. the region of the satellites on the acrocentric chromosomes that is active in nucleolus formation. SYN: nucleolar zone, nucleolus o.. nucleolus o. SYN: nucleolar o.. primary o. the o. situated on the dorsal lip of the blastopore. procentriole o. SYN: deuterosome.

Organ; organic. [G. organon]

organoaxial (or-ga′no-aks′e-al)
Rotation around the long axis of the organ; a type of gastric volvulus.

organoferric (or′ga-no-far′ik)
Relating to an organic compound containing iron.

organogel (or-gan′o-jel)
A hydrogel with an organic liquid instead of water as the dispersion means.

organogenesis (or′ga-no-jen′e-sis)
Formation of organs during development. SYN: organogeny. [organo- + G. genesis, origin]

organogenetic, organogenic (or′ga-no-je-net′ik, -jen′ik)
Relating to organogenesis.

organogeny (or-gan-oj′e-ne)
SYN: organogenesis.

organography (or′ga-nog′ra-fe)
A treatise on, or description of, the organs of the body. [organo- + G. graphe, a writing]

organoid (or′ga-noyd)
1. Resembling in superficial appearance or in structure any of the organs or glands of the body. 2. Composed of glandular or organic elements and not of a single tissue; pertaining to certain neoplasms ( e.g., an adenoma) that contain cytologic and histologic elements arranged in a pattern that closely resembles or is virtually identical to a normal organ. SEE ALSO: histoid. 3. SYN: organelle. [organo- + G. eidos, resemblance]

organoleptic (or′ga-no-lep′tik)
1. Stimulating any of the organs of sensation. 2. Susceptible to a sensory stimulus. [organo- + G. leptikos, disposed to accept]


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